Defense Secretary Caspar W. Weinberger hinted today that the United States will sell weapons to China if the Soviet Union intervenes in Poland.

"There's no linkage yet" between Soviet actions and the Reagan administration's position on arms sales to China, Weinberger told reporters traveling with him on a swing through Britain, West Germany and Italy.

An aide to Weinberger then added that the word "yet" should be underlined.

The Weinberger statement together with the emphasis placed on it suggest a Reagan administration attempt to signal Moscow that the United States may play the China card if Soviet troops march into Poland to suppress the independent labor movement.

This is believed to be the first Reagan administration allusion to such a move. Sen. Charles Percy (R-Ill.), chairman of the Senate Foreign Relations Committee, said in a televised interview last Sunday that he has "reason to believe" the Carter administration asked the Defense Department in December to draw up a list of weapons that "possibly would be sold or provided" to China "if force was used by the Soviet Union in Poland."

Sen. Ted Stevens (R-Alaska) said on a visit to Peking in January that he would not "rule out" arms sales there in view of Soviet "aggressiveness" in Poland.

Former president Jimmy Carter's national security adviser, Zbigniew Brzezinski, said after leaving office that a Soviet invasion of Poland could lead to an encircling alliance of China, Japan, Western Europe and the United States.

A senior official on the Weinberger plane, who declined to be identified, said Soviet suppression in Poland might also take the form of a forceful replacement of the current communist government there rather than a full-scale military invasion.

Either way, the U.S. intelligence community indicates a belief that the Kremlin is on the verge of major decisions on Poland, perhaps including whether to seize control militarily.

The escalating rhetoric by Weinberger and other administration officials seems to be designed to influence that decision.

Although the defense secretary did not say so, part of the administration's concern about an imminent military thrust stems from interceptions of radio communications revealing an intensive effort to get Soviet military units in and around Poland ready to move. This follows prolonged Warsaw Pact maneuvers in and around Poland.

Asked if stepped-up flights of Soviet transports in and out of Poland constitutes the kind of airlift that would be the prelude to direct military action, Weinberger hedged in these words: "There's a lot of activity which has been going on in connection with the maneuvers, which looks like it is consistent with an expansion of the maneuvers. We don't have any indication yet."

Asked at another point in a plane-side press conference here whether the Polish situation looked any more dangerous today than yesterday, the defense secretary replied: "I don't think so. There's still a very high level of activity which is still cause for considerable concern. . . . It's more activity than seems to be required for maneuvers that were supposed to have ended last week."

If Moscow opts for military action, Weinberger told reporters traveling with him, it cannot count on Polish soldiers to join the suppression. "I don't see the Polish Army firing on the Polish people."

If the Polish Army remained in its barracks while Soviet troops invaded, Weinberger predicted, Polish civilians, would put up a fight.

"I think their instinct is to do so," he said. "They always have in the past. They're a very proud and very freedom-loving people."

A senior official on Weinberger's plane said Poland's already dark economic picture is becoming darker.

The Poles, the official said, "are urgently, desperately in need of food." They will be out of some staples within 15 days unless they receive emergency help, he said. The Reagan administration, the official added, would like to help but is having difficulty doing so.

In another development, U.S. intelligence officials report that the Kremlin has ordered some military units out of Afghanistan.

One speculation is that Soviet supply lines have become overextended as they keep troops in a high state of readiness in and around Poland at the same time they are fighting on the ground in Afghanistan.

Weinberger, asked why he left Washington when the Polish situation looked so perilous and President Reagan was in the hospital, said his Boeing 707 is fully equiped with communications gear to keep in touch with command centers in the U.S. capital.

If the defense secretary's presence should be demanded in Washington, continued Weinberger with a smile "we've got a rudder. We can turn around."